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    <div>jiajiechishi</div>
     <div>   
        <ul>
            <li>1111</li>
            <li>2222</li>
            <li id='xx'>1111</li>
            <li>1111</li>
            <li>1111</li>
        </ul>
    </div>

</body>
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<h2>This is a top title</h2>
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<button>改变背景颜色</button>
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